The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present invention but provided by the invention. Some of such contributions of the invention may be specifically pointed out below, whereas other such contributions of the invention will be apparent from their context.
With the ever increasing demand for increasing data rates and higher quality services in the world of mobile communications comes ever increasing demand for better performance of cellular network infrastructures. The increased spectrum requirements due the increased data traffic drives operators seek offloading solutions for their traffic via local nodes providing local access to the Internet to prevent congesting own core network. A wide variety of diverse size of cells and connected devices are proposed in addition to traditional macro and microcells. However, the available frequency resources are limited and need for efficient use of the resources is essential.
Traditional solutions to improve spectrum efficiency cannot support the predicted data traffic in the future. Thus, operators, network and device manufacturers and other players in the field are considering the utilization of license-exempt (LE) or unlicensed frequency bands along with costly licensed spectrum. The LE spectrum can also be called as shared spectrum. Shared spectrum is only lightly regulated; users do not need licenses to exploit them. From the cellular traffic point of view, an interesting shared spectrum band opportunity is Industrial, Scientific and Medical (ISM) bands. The ISM bands are widely used for WLAN and Bluetooth® communication, for example. The ISM bands allow both standardized systems and proprietary solutions to be deployed onto spectrum as far as regulations are followed. The regulations define maximum transmission powers and certain rules for systems for the operation on the band.
Currently it is challenging to for many cellular systems such as the third and fourth generation systems long term evolution (LTE, known also as E-UTRA) and long term evolution advanced (LTE-A) to utilise ISM bands for example due to required continuous and synchronous resource allocation for control channels both in downlink and uplink transmission directions.